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Generators & Motors General DiscussionAntique Generators, Light Plants and Old Electric Motors: Questions and answers about restoring and showing old power generation systems.

Greetings...I recieved an 80's vintage homelite generator (MDL E3000-1A, UT 03595) when I recently bought the family farm. It's powered by a B&S Engine that starts easily and runs well. The one thing it won't do is generate electricity.

So far I've clean up & reseated the brushes, replaced the bridge rectifier (p/n EDI 0548 is the replacement number for the old one), & flashed the field with a 6 volt battery to the + & - brush terminals.

There doesn't appear to be any breakers to reset. The innards appear to be clean...I don't know a whole lot about these things but I'm learning fast and it's an interesting project.

Did it generate while flashing? if you did this stopped, if you can do it safely, while running at rated speed, and see if it makes voltage while it is being flashed, that will tell if the main alternator field and stator is in good condition.

Another thing is to measure the residual voltage on the output leads while running at rated speed not flashing or anything. If it's a 120/240 3 wire output, measure both hot leads to the neutral (120V?)and compare and then measure between the two hots (240?) and see if it's 2x the line to neutral measurement. The absolute level of residual voltage is important since the exciter needs some minimum voltage to build up to rated voltage output. The balance of voltages can point to miswiring and or shorted windings. If it's only 120 rated, then there is no balance If it is either 120/240, reconnectable, (2 windings, 4 wires), you can separate the 2 windings and check the voltage across each one and compare.

With the set stopped, lift the brushes and put a piece of paper under them and then measure the resistance from slip ring to slip ring (a few ohms) and also check from slip ring to shaft (infinity?).

Lots of things to check, be careful 'cause it might just start working

I would give it another shot with a 12 volt battery. If it does not put out anything then...it is probably the end of the line.

Make sure to check for power upstream of the plug since a wire or the outlet itself could have issues.

But other than that...you are probably looking at a rotor or stator or both.

Check the resistance of the stator windings and make sure none of them are grounded. Also check the resistance of the Rotor through the brushes...it shouldnt be much more than the going to the slip rings themselves. If nothing is shorted or open you could do a rotor current draw test.

But as I said earlier, if you put 12 volts to it with it running and get no power its either gonna be a rotor, stator or both...which I would think are not worth putting into something like that unless it has some kind of special meaning to you

Last night I marked and disconnected all leads going to the 110 and 220 outlets. The 4 leads coming from the stator are labeled T1 - T4. I got continuity between T1 & T2 and T3 & T4 but not any other combinations...I also disconnected, tested and got continuity for the two AC wires going from the rectifier to the stator...to my knowledge, this looks good.

Then I pulled the stator off the rotor and tried putting 6 volts to the contacts going to the coils. My theory was this should magnetize the rotor and I should be able to 'test' the magnetism with a nail or some other object...I couldn't get any part of the rotor to behave like a magnet. I switched to a 12 volt battery but got same results...My question is, should I be able to create a magnet out of the rotor by applying voltage in this way or am I barking up the wrong tree?

[QUOTE=Jim Rankin]
With the set stopped, lift the brushes and put a piece of paper under them and then measure the resistance from slip ring to slip ring (a few ohms) and also check from slip ring to shaft (infinity?).
QUOTE]

Jim...I checked the resistance between the slip rings at lunch, I get the same read (infinity) between the two slip rings that I get from slip ring to shaft which indicates no connectivity, right? I do show connectivity between each slip ring and it's corresponding coil wire on the rotor though. Does this makes sense?

If you magnetize the stator by touching the stator leads with DC, use a magnetic compass and you will see the evidence of the magnetic field that is created in the stator. There is enough leakage that the weak field you created will not effectively cross the airgap and magnetize the rotor.Still I would assume you should create a little stronger magnetic field with your 12v battery unless the resistance of the wire is so high the current (which makes the magnetic field) is just too low to work.

Do the output leads connect to the stator or the brushes? Most common is output from the stator, but there are some sets that have the output from the rotor and the field is stationary. Try magnetizing the rotor directly through the slip rings since it is the part that is (usually) made to magnetize.

If it was 3 phase and you had the correct 3 phase voltage available, you could test the stator by placing a ball bearing in the stator and bumping it with 3 phase AC to make the ball bearing follow the rotating magnetic field around the stator.

With single phase there isn't a real rotating magnetic field, more like an oscillating field. Single phase would be like a bicycle pedal crank with force mainly going back and forth in one plane compared to 3 phase which is more like a rotary aircraft engine with the power strokes following the crank around the circle. Either design will make the motor rotate, but the bicycle has to have some kind of rotary kick to make it start.

With the set stopped, lift the brushes and put a piece of paper under them and then measure the resistance from slip ring to slip ring (a few ohms) and also check from slip ring to shaft (infinity?).
QUOTE]

Jim...I checked the resistance between the slip rings at lunch, I get the same read (infinity) between the two slip rings that I get from slip ring to shaft which indicates no connectivity, right? I do show connectivity between each slip ring and it's corresponding coil wire on the rotor though. Does this makes sense?

Yes

There should normally be one circuit in the rotor, it should show continuity from one slipring to the other. Are you saying each slipring is continuous with the wire running back along the shaft to the steel stator pole pieces the coils are wound on? Sounds like you don't have a circuit in the rotor from one slip ring to the other. if you can find a break, and carefully reconnect, resecure and revarnish the coil, you can fix it. You aren't dealing with a lot of voltage, but you do have to contend with centrifugal forces, so it has to be secure when you're all done.

If there are more than 2 slip rings and or a segmented commutator, things are more complicated and we probably would need pictures, but sounds to me like you have found the problem

Are you saying each slipring is continuous with the wire running back along the shaft to the steel stator pole pieces the coils are wound on? Sounds like you don't have a circuit in the rotor from one slip ring to the other.

If you magnetize the stator by touching the stator leads with DC, use a magnetic compass and you will see the evidence of the magnetic field that is created in the stator. There is enough leakage that the weak field you created will not effectively cross the airgap and magnetize the rotor.Still I would assume you should create a little stronger magnetic field with your 12v battery unless the resistance of the wire is so high the current (which makes the magnetic field) is just too low to work.

Are you saying I should put the 6 or 12 volt dc to the output leads going to the outlets to create the magnetic field?

Do the output leads connect to the stator or the brushes? Most common is output from the stator, but there are some sets that have the output from the rotor and the field is stationary.I believe the output leads come from the stator assuming the stator is the housing that the rotor rotates inside

Try magnetizing the rotor directly through the slip rings since it is the part that is (usually) made to magnetize.I think this is what I attempted last night except I connected the DC to the two leads that go to the coils on the rotor...If I instead put the DC to the slip rings would this make any difference?

If it was 3 phase and you had the correct 3 phase voltage available, you could test the stator by placing a ball bearing in the stator and bumping it with 3 phase AC to make the ball bearing follow the rotating magnetic field around the stator.

With single phase there isn't a real rotating magnetic field, more like an oscillating field. Single phase would be like a bicycle pedal crank with force mainly going back and forth in one plane compared to 3 phase which is more like a rotary aircraft engine with the power strokes following the crank around the circle. Either design will make the motor rotate, but the bicycle has to have some kind of rotary kick to make it start.

""""Are you saying I should put the 6 or 12 volt dc to the output leads going to the outlets to create the magnetic field?"""

No, I thought from your description you had flashed the stator circuits with your batteries. Magnetizing the rotor (also called the armature or field) is what you want to do. The fact that it didn't magnetize and you have no continuity between the two slip rings means the circuit is open somewhere in the field. maybe with some close inspection you can find the break.

"""""I connected the DC to the two leads that go to the coils on the rotor...If I instead put the DC to the slip rings would this make any difference? """""

No, shouldn't make any difference if the leads are connected to the sliprings like they are supposed to be.

Jim...I took a close look today and found a small hole in the winding that looked like it had been burned there. It was definately the cause for no continuity between the slip rings. Question is, where do I go from here?

There is a number on the rotor, its A 461142. It seems my options are buy new (if possible), have it rewound or fix this myself... What would you suggest?

I would see if you can take something like a blunt knife (table knife maybe) and gently separate the windings and isolate the break(s). If you're lucky you can splice with a soldering iron, wrap with paper to separate from the ones next to it and keep it from shorting where the insulation is damaged. Then check continuity again and if ok, varnish with polyurethane to insulate and bond the winding back together.

If the damage is deep or extensive, It can be rewound. You could do it or send it to an electric motor repair shop for a professional job. The rotor is a lot simpler than an electric motor since there is only one circuit, so you can unwind, counting turns and recording how it is wound so you can go back the same way. "magnet wire" is available on ebay most all the time if you can tell what gauge you need by measuring with a caliper you can usually find what you need. The best way to varnish and bake it when you're through would be to take it to the motor shop and let them do it or you can do it, but it would be messy, stinky and I don't know where you could buy the right varnish to do the whole thing with. Polyurethane might be fine, I don't know.

If you want to find the gauge, I have a table somewhere to look it up if you can measure the diameter of the wire including the enamel insulation. That information should be on the net somewhere as well.

I was able to seperate the windings and find the break...when I put a jumper across the break and checked resistance at the slip rings the needle jumped to around 3 ohms, so I think this means I just have one break...Is this correct?

While I was seperating the windings, I scraped insulation off a small section of the wire near the break but did not create a new break. Can I just use polyurethane to re-insulate this area? Do I just use common polyurethane wood varnish?

If so I think I can solder the break and repair as you describe and see what happens when I put it back together and fire it up. Worst case, I take it to a shop to be rewound...

The poly should be fine on a small area like that. You might want to use some paper around your splice to give it some extra thickness of insulation since it wouldn't be so smooth. brush the poly in well around the splice and paper and then let it dry thoroughly and potentially put it under a lamp to bake hard after it gets dry to the touch. make sure it can't burn from the lamp if you do go that route.